System for providing an electrical activity map using optical shape sensing

ABSTRACT

The invention relates to a system ( 1 ) for providing an electrical activity map of the heart by means of electrical signals acquired by a plurality of surface electrodes ( 9 ). A surface electrodes positions determination unit ( 4, 6, 13 ) determines positions of the plurality of surface electrodes by means of optical shape sensing localization. The optical shape sensing element may comprise a wand ( 4 ), or alternatively an optical shape sensing fiber embedded in the vest comprising the surface electrodes. The position of a cardiac structure may be determined using ultrasound. An electrical activity map determination unit ( 16 ) determines the electrical activity map at the cardiac structure based on the measured electrical signals, the determined positions of the plurality of electrodes and the position of the cardiac structure, in particular, of the epicardial surface. Since optical shape sensing is used for determining the positions of the plurality of surface electrodes and not, for instance, x-rays, the electrical activity map can be determined, without necessarily applying an x-ray radiation dose.

FIELD OF THE INVENTION

The invention relates to a system, a method and a computer program forproviding an electrical activity map of the heart of a living being bymeans of electrical signals from the heart acquired by a plurality ofsurface electrodes being arranged on an outer surface of the livingbeing. The invention relates further to a vest comprising the pluralityof surface electrodes.

BACKGROUND OF THE INVENTION

The article “Noninvasive Characterization of Epicardial Activation inHumans With Diverse Atrial Fibrillation Patterns” by P. S. Cuculich etal., Circulation, Journal of the American Heart Association, 122, pages1364 to 1372 (2010) discloses a system comprising an electrode vest withsurface electrodes for measuring electrical potentials on an outersurface of a person. The system further comprises a reconstruction unitfor reconstructing epicardial electrical potentials based on i) aspatial relation between the heart surface and the surface electrodes onthe outer surface of the person and ii) the measured electricalpotentials. The spatial relation between the heart surface and thesurface electrodes on the outer surface of the person are obtained byacquiring an x-ray computed tomography image showing both, the heartsurface and the surface electrodes on the outer surface of the person.By acquiring the x-ray computed tomography image a relatively highradiation dose is applied to the person.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system, a methodand a computer program for providing an electrical activity map of theheart of a living being by means of electrical signals from the heartacquired by a plurality of surface electrodes being arranged on an outersurface of the living being, wherein the radiation dose applied to theperson can be reduced, in particular, can be eliminated. It is a furtherobject of the present invention to provide a vest for being worn by aliving being and for being used for providing the electrical activitymap.

In a first aspect of the present invention a system for providing anelectrical activity map of the heart of a living being by means ofelectrical signals from the heart acquired by a plurality of surfaceelectrodes being arranged on an outer surface of the living being ispresented, the system comprising:

a surface electrodes positions determination unit for determiningpositions of the plurality of surface electrodes by means of opticalshape sensing localization,

a cardiac structure position determination unit for determining aposition of a cardiac structure of the living being,

an electrical activity map determination unit for determining theelectrical activity map at the cardiac structure based on the electricalsignals measured on the outer surface of the living being, thedetermined positions of the plurality of electrodes and the determinedposition of the cardiac structure.

Since the positions of the plurality of surface electrodes aredetermined by means of optical shape sensing localization, thesepositions can be determined without necessarily acquiring a computedtomography image showing the plurality of surface electrodes. Thisallows reducing, in particular, eliminating, the x-ray radiation doseapplied to the living being for generating an electrical activity map ofthe heart.

The cardiac structure is preferentially the epicardial surface of theheart.

If the cardiac structure is three-dimensional, in particular, if thecardiac structure is the three-dimensional epicardial surface, theposition of the cardiac structure preferentially defines the position ofeach point of the cardiac structure at which the electrical activity mapshould be determined. Thus, for instance, if the cardiac structureposition determination unit determines the position of the epicardialsurface, it determines at least the positions of the points on theepicardial surface for which an electrical potential should bedetermined for generating the electrical activity map.

The plurality of surface electrodes can be regarded as being an elementof the system or it can be regarded as being a separate element, whereinthe system is adapted to use the electrical signals of the surfaceelectrodes for providing the electrical activity map.

The plurality of surface electrodes can be incorporated in a vest thatcan be worn by the living being. The living being is preferentially aperson, but the living being can also be an animal.

The cardiac structure position determination unit comprisespreferentially an ultrasound unit for generating an ultrasound signalbeing indicative of the position of the cardiac structure and a cardiacstructure position calculation unit for calculating the position of thecardiac structure based on the ultrasound signal. The ultrasound unit ispreferentially a transthoracic echo probe or a transesophageal echoprobe. If the ultrasound unit is a transthoracic echo probe or atransesophageal echo probe, an ultrasound image of the heart showing theepicardial surface can be acquired with high quality, thereby allowingthe cardiac structure position calculation unit to determine theposition of the epicardial surface being the preferred cardiac structurewith high accuracy.

In an embodiment the cardiac structure position calculation unit isadapted to perform a segmentation procedure for segmenting the cardiacstructure in the ultrasound image for detecting the cardiac structure.In another embodiment the cardiac structure position calculation unit isadapted to provide an anatomical cardiac model being an anatomical modelof a heart including the cardiac structure and to adjust the cardiacmodel to the ultrasound image of the heart for detecting the cardiacstructure. The adjustment can just be a rotation and/or translation andoptionally a scaling of the cardiac model, or it can also include adeformation of the cardiac model. The cardiac model is preferentially ageneralized cardiac model, i.e. a cardiac model which is, before beingadjusted, not specific for a certain person or animal. It can bedetermined by, for instance, averaging segmented hearts of a group ofliving beings, which may be segmented in medical images.

It is further preferred that the ultrasound unit is equipped with anoptical shape sensing sensor for generating an optical shape sensingsignal being indicative of the position of the ultrasound unit, whereinthe cardiac structure position calculation unit is adapted to determinethe position of the cardiac structure based on the optical shape sensingsignal and the ultrasound signal. The optical shape sensing sensor ispreferentially an optical shape sensing fiber, which may be partlyarranged within the ultrasound unit. This allows determining theposition of the ultrasound unit by optical shape sensing, withoutapplying, for instance, x-rays to the person. In particular, if theultrasound signal represents an ultrasound image of the heart, theepicardial surface in the ultrasound image can be segmented fordetermining the position of the epicardial surface within the ultrasoundimage and this determined position of the epicardial surface can berelated to a reference position, i.e. it can be determined within areference coordinate system, based on the position of the ultrasoundunit known from the optical shape sensing signal.

In an embodiment the surface electrodes positions determination unitcomprises a spatial relation providing unit for providing spatialrelations between the positions of the plurality of surface electrodesand positions of reference marks, wherein the ultrasound unit is adaptedto be brought into contact with the reference marks, wherein the opticalshape sensing sensor is adapted to generate a respective optical shapesensing signal while being in contact with a respective reference markfor generating an optical shape sensing signal being indicative of theposition of the respective reference mark, and wherein the surfaceelectrodes positions determination unit comprises a surface electrodespositions calculation unit for calculating the positions of the surfaceelectrodes depending on the optical shape sensing signals and thespatial relations. Thus, the ultrasound unit can be used for twopurposes, determining the position of the cardiac structure anddetermining the positions of the plurality of surface electrodes. Thisreduces the number of elements needed for determining the electricalactivity map of the heart.

In an embodiment the surface electrodes positions determination unitcomprises a) a spatial relations providing unit for providing spatialrelations between the positions of the plurality of surface electrodesand positions of reference marks, b) an optical shape sensing elementfor generating an optical shape sensing signal being indicative of theposition of the tip of the optical shape sensing element while being incontact with a respective reference mark, in order to generate anoptical shape sensing signal being indicative of the position of therespective reference mark, and c) a surface electrodes positionscalculation unit for calculating the positions of the surface electrodesdepending on the optical shape sensing signal and the spatial relations.The optical shape sensing element can comprise a wand and an opticalshape sensing fiber connected to the wand, wherein the tip of theoptical shape sensing element is the tip of the wand. Thus, a user cantouch the reference marks with the wand and determine the positions ofthe reference marks by determining the positions of the tip of the wand,while the tip is brought into contact with the different referencemarks. The optical shape sensing element can be adapted to, for example,continuously generate an optical shape sensing signal, or to generate anoptical shape sensing signal only after a user has requested an opticalshape sensing signal via an input unit like a button to be pressed. Thetip can also be provided with a pressure sensitive sensor for detectingwhether the tip is in contact with an element or not, wherein theoptical shape sensing element can be adapted to generate an opticalshape sensing signal, when the pressure sensitive sensor detects thatthe tip is in contact with a reference mark.

The system can further comprise a movement determination unit fordetermining a movement of the living being, wherein the surfaceelectrodes positions determination unit can be adapted to determine thepositions of the plurality of surface electrodes depending on thedetermined movement. The movement determination unit can comprise anoptical shape sensing sensor for being attached to the living being atan attachment location and for generating an optical shape sensingsignal being indicative of an actual position of the optical shapesensing sensor and a movement calculation unit for calculating amovement of the living being depending on the generated optical shapesensing signal. One or several optical shape sensing sensors can be usedfor determining the movement of the living being. The optical shapesensing sensors can be adapted to be directly attached to the livingbeing or to be attached to another means being attached to the livingbeing. The other means can be, for instance, a vest comprising theplurality of the surface electrodes or patches that can be put on, forexample, a person's thorax. Considering a possible movement of theperson while determining the electrical activity map of the heart canreduce corresponding possible inaccuracies in the electrical activitymap.

In an embodiment the surface electrodes positions determination unitcomprises a) an optical shape sensing sensor for generating opticalshape sensing signals being indicative of the position of the opticalshape sensing sensor, b) a spatial relation providing unit for providingspatial relations between the positions of the optical shape sensingsensor and the positions of the surface electrodes, and c) a surfaceelectrodes positions calculation unit for calculating the positions ofthe surface electrodes depending on the generated optical shape sensingsignals and the spatial relations. In this embodiment the optical shapesensing sensor can be incorporated into a vest which also comprises theplurality of surface electrodes, wherein the spatial relations betweenthe optical shape sensing sensor and the plurality of surface electrodesare known and stored in the spatial relation providing unit. This allowsdetermining the positions of the surface electrodes without using, forinstance, an optical shape sensing wand touching the different surfaceelectrodes. For instance, an electrical activity map can be generatedjust by using the vest with the one or several optical shape sensingsensors and an ultrasound unit also being equipped with an optical shapesensing sensor such that the position of the ultrasound unit relative tothe surface electrodes can be determined by optical shape sensing,preferentially without requiring further means for determining thepositions of the surface electrodes and the cardiac structure. Sinceless elements are needed for generating the electrical activity map, theprocess for determining the electrical activity map to be performed by,for instance, a physician can be simplified.

In a further aspect of the present invention a vest for being worn by aliving being is presented, the vest being adapted to be used forproviding an electrical activity map, the vest comprising:

a plurality of surface electrodes for being arranged on an outer surfaceof the living being, when the vest is worn by the living being, and foracquiring electrical signals from the heart of the living being,

an optical shape sensing sensor for generating an optical shape sensingsignal being indicative of the position of the optical shape sensingsensor and for providing the optical shape sensing signal to a surfaceelectrodes positions determination unit.

In a further aspect of the present invention a method for providing anelectrical activity map of the heart of a living being by means ofelectrical signals from the heart acquired by a plurality of surfaceelectrodes being arranged on an outer surface of the living being ispresented, the method comprising:

determining positions of the plurality of surface electrodes by means ofoptical shape sensing localization by a surface electrodes positionsdetermination unit,

determining a position of a cardiac structure of the living being by acardiac structure position determination unit,

determining the electrical activity map at the cardiac structure basedon the electrical signals measured on the outer surface of the livingbeing, the determined positions of the plurality of electrodes and thedetermined position of the cardiac structure by an electrical activitymap determination unit.

In a further aspect of the present invention a computer program forproviding an electrical activity map of the heart of a living being bymeans of electrical signals from the heart acquired by a plurality ofsurface electrodes being arranged on an outer surface of the livingbeing is presented, the computer program comprising program code meansfor causing a system as defined in claim 1 to carry out the steps of themethod as defined in claim 12, when the computer program is run on acomputer controlling the system.

It shall be understood that the system of claim 1, the method of claim12 and the computer program claim 13 have similar and/or identicalpreferred embodiments, in particular, as defined in the dependentclaims.

It shall be understood that a preferred embodiment of the invention canalso be any combination of the dependent claims with the respectiveindependent claim.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

FIG. 1 shows schematically and exemplarily an embodiment of a system forproviding an electrical activity map of the heart of a living being,

FIG. 2 shows schematically and exemplarily a further embodiment of asystem for providing an electrical activity map of the heart of theliving being, and

FIG. 3 shows a flowchart exemplarily illustrating an embodiment of amethod for providing an electrical activity map of the heart of a livingbeing.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows schematically and exemplarily an embodiment of a system forproviding an electrical activity map of the heart of a living being bymeans of electrical signals from the heart acquired by a plurality ofsurface electrodes being arranged on an outer surface of the livingbeing. The system 1 comprises an optical shape sensing element 4, 6 forgenerating an optical shape sensing signal being indicative of theposition of the tip 17 of the optical shape sensing element 4, 6 whilebeing in contact with a respective reference mark 2, in order togenerate an optical shape sensing signal being indicative of theposition of the respective reference mark 2. In particular, the livingbeing 30 being, in this embodiment, a person wears a vest 8 with surfaceelectrodes 9 and reference marks 2. A user like a physician can use theoptical shape sensing element 4, 6 such that the tip of the opticalshape sensing element 4, 6 consecutively touches the different referencemarks 2 of the vest 8, in order to determine the positions of thereference marks 2. The vest 8 is electrically connected with adetermination system 11 via an electrical connection 25, in order totransmit the electrical signals acquired by the surface electrodes 9 tothe electrical activity map determination unit 16.

The optical shape sensing element 4, 6 comprises a wand 4, which can beheld by a hand 5 of a user, with the tip 17 for being brought in contactwith different reference marks 2 and an optical shape sensing fiber 6being connected to the wand 4. The optical shape sensing element 4, 6can be adapted to, for example, continuously generate an optical shapesensing signal or to generate an optical shape sensing signal only aftera user has requested an optical shape sensing signal via an input unitlike a button to be pressed. The tip can also be provided with apressure sensitive sensor for detecting whether the tip is in contactwith an element or not, wherein the optical shape sensing element can beadapted to generate an optical shape sensing signal, when the pressuresensitive sensor detects that the tip is in contact with a referencemark.

The system 1 comprises a further optical shape sensing element, i.e. anoptical shape sensing sensor 7, 26 for being attached to the person 30at an attachment location and for generating an optical shape sensingsignal being indicative of the actual position of the optical shapesensing sensor 7, 26. In this embodiment this optical shape sensingsensor comprises a reference patch 7 connected to an optical shapesensing fiber 26, wherein the generated optical shape sensing signal isindicative of the position of the reference patch 7.

The optical shape sensing signal from the optical shape sensing sensor7, 26, which is indicative of the position of the reference patch 7, andthe optical shape sensing signal from the optical shape sensing element4, 6, which is indicative of the position of the tip 17 of the opticalshape sensing element 4, 6, are provided to a surface electrodespositions calculation unit 13 of the determination system 11. Thesurface electrodes positions calculation unit 13 is adapted to determinethe three-dimensional positions of the reference marks 2 with respect tothe reference patch 7 based on the provided optical shape sensingsignals. For determining the positions of the reference marks 2 knownoptical shape sensing localization method can be used like the opticalshape sensing methods disclosed in WO 2011/141830 A1, which is herewithincorporated by reference.

After the positions of the reference markers 2 have been determined, thesurface electrodes positions calculation unit 13 determines thepositions of the surface electrodes 9 depending on the determinedpositions of the reference marks 2 and known spatial relations betweenthe positions of the plurality of surface electrodes 9 and the positionsof the reference marks 2 provided by a spatial relation providing unit12.

Thus, the wand 4 with the optical shape sensing fiber 6 is used tomeasure the positions of the reference marks 2 in the three-dimensionalspace with respect to the reference patch 7. By going from one referencemark 2 to another reference mark 2 and recording the three-dimensionalpositions, a three-dimensional distribution of the reference marks 2 andthus, since the spatial relations between the reference marks 2 and thesurface electrodes 9 being connected by tortuous wires 3 are known, thethree-dimensional distribution of the vest electrodes can bereconstructed. The wand 4 with the optical shape sensing fiber 6, thespatial relations providing unit 12 and the surface electrodes positionscalculation 13 can therefore be regarded as being components of asurface electrodes positions determination unit for determining thepositions of a plurality of surface electrodes by means of optical shapesensing localization.

The system 1 further comprises an ultrasound unit 22 for generating anultrasound signal being indicative of the position of the cardiacstructure within the person 30. The ultrasound signal is provided to thedetermination system 11 via the electrical connection 15. In thisembodiment the ultrasound unit is a transthoracic echo probe 22 forgenerating an ultrasound signal representing a three-dimensionalultrasound image of the heart. In another embodiment the ultrasound unitcan also be another probe like a transesophageal echo probe.

The ultrasound signal is provided to a cardiac structure positioncalculation unit 14 for calculating the position of the cardiacstructure based on the ultrasound signal. In particular, the cardiacstructure calculation unit 14 is adapted to detect the cardiac structurein the ultrasound image and to calculate the position of the cardiacstructure based on the cardiac structure detected in the ultrasoundimage. For instance, the cardiac structure position calculation unit 14can be adapted to perform a segmentation procedure for segmenting thecardiac structure being, in this embodiment, the epicardial surface, inthe ultrasound image for detecting the cardiac structure. The cardiacstructure position calculation unit can also be adapted to provide ananatomical cardiac model being an anatomical model of a heart includingthe cardiac structure, i.e. in this embodiment including the epicardialsurface, and to adjust the cardiac model to the ultrasound image of theheart for detecting the cardiac structure. The cardiac model ispreferentially a generalized cardiac model, i.e. a cardiac model whichis, before being adjusted, not specific for a certain person or animal.It can be determined by, for instance, averaging of segmented hearts ofa group of living beings, which may be segmented in medical images. Inorder to allow the cardiac structure position calculation unit tocalculate the position of the detected cardiac structure, the cardiacstructure position calculation unit 14 further receives an optical shapesensing signal from the ultrasound unit 22. The ultrasound unit 22 isequipped with an optical shape sensing sensor 10 for generating theoptical shape sensing signal being indicative of the position of theultrasound unit 22, wherein the cardiac structure position calculationunit 14 is adapted to determine the position of the ultrasound unit 22with respect to the position of the reference patch 7 based on theoptical sensing signals received from the optical shape sensing sensor10 of the ultrasound unit 22, which is an optical shape sensing fiber,and from the optical shape sensing sensor comprising the reference patch7 and the optical shape sensing fiber 26 connected to the patch 7. Theposition of the cardiac structure, i.e. in this embodiment of theepicardial surface, is then determined based on the determinedthree-dimensional position of the ultrasound unit 22 and the determinedposition of the cardiac structure within the ultrasound image acquiredby the ultrasound unit 22.

Thus, an ultrasound probe 22 with an optical shape sensing fiber 10 isused to image the cardiac anatomy, wherein the optical shape sensingfiber 10, which is preferentially embedded in the ultrasound probe 22,is used to measure the location of the ultrasound probe 22 with respectto the reference patch 7, thus ensuring that the location of the cardiacanatomy as imaged by the ultrasound probe 22 and the positions of thesurface electrodes 9 in three-dimensional space are known with respectto each other. In other words, since in this embodiment the positions ofthe surface electrodes 9 and of the epicardial surface are determinedwith respect to the same reference being the reference patch 7, thespatial relation between the surface electrodes 9 and the epicardialsurface is known. In other embodiments, the positions of the surfaceelectrodes and the position of, for instance, the epicardial surface canbe determined with respect to another reference. The optical shapesensing sensor 10, the cardiac structure position calculation unit 14and the ultrasound unit 22 with the electrical connection 15 fortransferring the ultrasound signal can be regarded as being elements ofa cardiac structure position determination unit for determining aposition of a cardiac structure like the epicardial surface of theperson 30.

The system further comprises a movement determination unit fordetermining a movement of the person 30, wherein the surface electrodespositions calculation unit 13 is adapted to determine the positions ofthe plurality of surface electrodes 9 also depending on the determinedmovement. The movement determination unit comprises a further patch 24,a further optical shape sensing fiber 23 attached to the patch 24 and amovement calculation unit 18. The movement calculation unit 18 receivesan optical shape sensing signal being indicative of the position of thefurther patch 24 attached to the vest 8, wherein for providing thisoptical shape sensing signal the patch 24 is connected with the opticalshape sensing fiber 23. The movement calculation unit 18 calculates theposition of the patch 24 at different times from the received opticalshape sensing signal, in order to determine the movement of the person30.

One or several optical shape sensing sensors, for instance, one orseveral patches with optical shape sensing fibers, can be used fordetermining the movement of the person 30. The optical shape sensingsensors for determining the movement of the person can be adapted to bedirectly attached to the person. For instance, the optical shape sensingsensors, in particular, patches connected to optical shape sensingfibers, can be put on a person's thorax. Alternatively or in addition,the optical shape sensing sensors can be attached to another means beingattached to the person. The other means can be, as shown in FIG. 1, avest comprising the plurality of surface electrodes.

The system 1 further comprises an electrical activity map determinationunit 16 for determining the electrical activity map at the cardiacstructure, i.e. in this embodiment on the epicardial surface, based onthe electrical signals measured on the outer surface of the person 30,the determined positions of the plurality of electrodes 9 and thedetermined position of the cardiac structure. For determining theelectrical activity map well known methods can be used like the methodsdisclosed in the article “Electrocardiographic Imaging (ECGI): ANoninvasive Imaging Modality for Cardiac Electrophysiology andArrhythmia” by Ramanathan et al., Nature Medicine 10, 422-428 (2004) ordisclosed in U.S. Pat. No. 7,471,971, which are herewith incorporated byreference. Moreover, known products from the companies CardioInsightTechnologies and Amycard can be used for determining the electricalactivity map at the cardiac structure, i.e. in this embodiment on theepicardial surface, based on the electrical signals measured on theouter surface of the person, the determined positions of the pluralityof electrodes and the determined position of the cardiac structure.

The determination system 11 further comprises an analysis unit 21 foranalyzing the electrical activity map for determiningelectrophysiological mechanisms of certain cardiac arrhythmias.Moreover, in addition or alternatively the analysis unit 21 may beadapted to analyze the electrical activity behaviour of cardiacdyssnychrony in heart failure patients as disclosed in the articles“Noninvasive Characterization of Epicardial Activation in Humans withDiverse Atrial Fibrillation Patterns” by P. S. Cuculich et al.,Circulation 122, 1364-1372 (2010), “Electrocardiographic Imaging ofVentricular Bigeminy in a Human Subject” by Y. Wang et al., CirculationArrhythmia and Electrophysiology 1, 74-75 (2008) and“Electrocardiographic Imaging of Cardiac Resynchronization Therapy inHeart Failure: Observations of Variable Electrophysiological Responses”by P. Jia et al., Heart Rhythm Journal 3, 296-310 (2006), which areherewith incorporated by reference.

In particular, the analysis unit can be adapted to perform at least oneof following analyses based on the electrical activity map:determination of an anatomical position of ectopi foci, determination ofan anatomical position of ventricular re-entries, distinguishing betweenre-entry or focal ventricular tachycardia and assessing of itslocalizations, assessing re-connection of pulmonary vein conduction andlocalization of culprit pulmonary veins, and assessment of effects ofantiarrhythmic drugs.

The electrical activity map of the heart and optionally results of theanalysis can be shown on a display unit 19.

FIG. 2 shows schematically and exemplarily a further embodiment of asystem for providing an electrical activity map of the heart of a livingbeing by means of electrical signals from the heart acquired by aplurality of surface electrodes being arranged on an outer surface ofthe living being. Also in this embodiment the living being is a person130 wearing a vest 108 with a plurality of electrodes 109 connected bytortuous wires 103. The surface electrodes 109 are used for acquiringelectrical signals at the outer surface of the person 130, wherein theacquired electrical signals are provided to a determination system 111via an electrical connection 125.

The vest 108 comprises an optical shape sensing fiber 107 for providingan optical shape sensing signal being indicative of the position of eachportion of the optical shape sensing fiber 107 within the vest 108. Anultrasound unit 122 with an optical shape sensing fiber 110 and anelectrical connection 115 for providing ultrasound signals to thedetermination system 111 is used for generating a three-dimensionalultrasound image of the heart of the person 130. The ultrasound unit 122with the optical shape sensing fiber 110 and the electrical connection115 is similar to the ultrasound unit 22 with the optical shape sensingfiber 10 and the electrical connection 15 described above with referenceto FIG. 1.

The determination system 111 comprises a spatial relation providing unit112 for providing a spatial relation between the optical shape sensingfiber 107 within the vest 108 and the surface electrodes 109. Thisspatial relation is used together with the optical shape sensing signal,which is provided by the optical shape sensing fiber 107 and which isindicative of the position of each portion of the optical shape sensingfiber 107 within the vest 108, for determining the position of thesurface electrodes 109 incorporated into the vest 108. Thus, the shapeof at least one optical shape sensing fiber 107, which is embedded in aspecific pattern in the vest 108, can be measured for determining theposition of each portion of the optical shape sensing fiber 107 withinthe vest 108. The locations of the surface electrodes 109 with respectto the optical shape sensing fiber 107 are known from the spatialrelation provided by the spatial relation providing unit 112. Therefore,a surface electrodes positions calculation unit 113 can calculate thethree-dimensional distribution of the surface electrodes 109 bymeasuring the three-dimensional shape of the optical fiber 107. Theoptical shape sensing fiber 107, the spatial relation providing unit 112and the surface electrodes positions calculation unit 113 can thereforebe regarded as being elements of a surface electrodes positionsdetermination unit for determining positions of the plurality of surfaceelectrodes 109 by means of optical shape sensing localization.

The determination system 111 further comprises a cardiac structureposition calculation unit 114 for calculating the position of thecardiac structure, i.e. in this embodiment of the epicardial surface,based on the optical shape sensing signal received from the vest opticalshape sensing fiber 107, the optical shape sensing signal received fromthe ultrasound optical shape sensing fiber 110 and the ultrasound signalacquired by the ultrasound unit 122. In particular, the ultrasoundsignal is a three-dimensional ultrasound image of the heart of theperson 130, wherein the cardiac structure position calculation unit 114is adapted to segment the epicardial surface in the three-dimensionalultrasound image for determining the position of the epicardial surfacewithin this image. The position of this epicardial surface with respectto the position of the surface electrodes 109 is then determined bydetermining the position of the ultrasound unit 122 with respect to theposition of the optical shape sensing fiber 107. Thus, the ultrasoundunit 122, which can be regarded as being an ultrasound probe wand, isused to image the cardiac anatomy, wherein the optical shape sensingfiber 110, which is embedded in the ultrasound unit 122, is used tomeasure the location of the ultrasound unit 122 with respect to theoptical shape sensing fiber 107 embedded in the vest 108, therebyensuring that the location of the cardiac anatomy, i.e. in thisembodiment of the epicardial surface, as imaged by the ultrasound unit122 and the position of the surface electrodes 109 are known in thethree-dimensional space. The optical shape sensing fiber 110, thecardiac structure calculation determination unit 114 and the ultrasoundunit 122 with the electrical connection 115 for transferring theultrasound signals can be regarded as being elements of a cardiacstructure position determination unit for determining a position of acardiac structure of the person 130.

The determination system 111 further comprises an electrical activitymap determination unit 116 and an analysis unit 121, which are similarto the electrical activity map determination unit 16 and the analysisunit 21, respectively, described above with reference to FIG. 1. Alsothe display unit 119 is similar to the display unit 19 described abovewith reference to FIG. 1.

In the following an embodiment of a method for providing an electricalactivity map of the heart of a living being by means of electricalsignals from the heart acquired by a plurality of surface electrodes atan outer surface of the living being will exemplarily be described withreference to a flowchart shown in FIG. 3.

In step 101, the positions of the plurality of surface electrodes aredetermined by the surface electrodes positions determination unit bymeans of optical shape sensing localization. For instance, the wand 4with the connected optical shape sensing fiber 6 described above withreference to FIG. 1 is used for determining the three-dimensionalpositions of reference marks of a vest worn by a person by using opticalshape sensing. A surface electrodes positions calculation unit can thencalculate the three-dimensional positions of the electrodes of the vestbased on the determined three-dimensional positions of the referencemarks and provided spatial relations between the reference marks and thesurface electrodes incorporated in the vest. Alternatively, an opticalshape sensing fiber 107 embedded in the vest worn by the person can beused for determining the three-dimensional position of the surfaceelectrodes as described above with reference to FIG. 2. In particular,the three-dimensional position of each portion of the optical shapesensing fiber 107 within the vest 108 can be determined by optical shapesensing, wherein the surface electrodes positions calculation unit cancalculate the three-dimensional positions of the surface electrodesbased on the determined three-dimensional position of each portion ofthe optical shape sensing fiber 107 within the vest 108 and a providedspatial relation between the optical shape sensing fiber within the vestand the surface electrodes embedded in the vest.

In step 102, the position of a cardiac structure of the person 30 isdetermined. In this embodiment the position of the epicardial surface isdetermined. For instance, the ultrasound unit with the optical shapesensing sensor described above with reference to FIGS. 1 and 2 is usedfor generating a three-dimensional ultrasound image showing theepicardial surface, wherein the cardiac structure position calculationunit can calculate the three-dimensional position of the epicardialsurface based on, for example, a segmentation of the epicardial surfacein the three-dimensional ultrasound image and the position of theultrasound unit determined by optical shape sensing localization. Steps101 and 102 can be performed in an arbitrary order, i.e. they can beperformed consecutively or simultaneously.

In step 103, the electrical activity map determination unit determinesthe electrical activity map at the cardiac structure, i.e., in thisembodiment, on the epicardial surface, based on the electrical signalsmeasured on the outer surface of the person, the positions of theplurality of surface electrodes determined in step 101 and the positionof the cardiac structure determined in step 102. In step 104, theanalysis unit analyzes the electrical activity map, in order todetermine, for example, electrophysiological mechanisms of certaincardiac arrhythmias. In step 105, the electrical activity map andoptionally also results of the analysis are shown on the display unit.

In the embodiment of the method for providing an electrical activity mapof the heart described above with reference to FIG. 3 it is assumed thatthe electrical signals on the outer surface of the person have beenmeasured already and are provided to the electrical activity mapdetermination unit for allowing the electrical activity mapdetermination unit to determine the electrical activity map. In anotherembodiment the measurement of the electrical signals on the outersurface of the person can also be a part of the method for providing theelectrical activity map, wherein in this case a corresponding electricalsignals measurement step is performed before step 103.

Electrocardiographic mapping (ECM) is a method where body surfacesignals, i.e. electrical signals like electrical potentials measured atthe outer surface of the person, which are measured by a multitude ofelectrodes covering the entire human thorax, are used to calculate theactivation of the epicardial surface of the heart. The electrodes aresurface electrodes, i.e. electrodes measuring electrical signals at thesurface of the person, and they are contained in the vest that istightly attached to the skin of the thorax by an adhesive. Alternativelyor in addition, the vest can comprise elastic textiles for tightlyfitting the vest to the skin of the thorax. Since the position of theepicardial heart surface and the positions of the surface electrodeshave been determined, the three-dimensional spatial relations betweenthe epicardial heart surface and the surface electrodes are known. Thisenables the electrical activity map determination unit to compute anaccurate single beat electrical activation pattern on the epicardialheart surface being the electrical activity map. The system describedabove with reference to FIG. 1 can therefore provide a non-invasivemethod for rapid assessment, i.e. within seconds to real time, ofcardiac electrical activation. This electrocardiographic mapping can beperformed, for example, during an electrophysiological procedure orduring interventional cardiology procedures in a correspondinglaboratory. However, the electrocardiographic mapping can also beperformed for pre-interventional or post-interventional follow-updiagnostic procedures. In particular, the electrocardiographic mappingcan be used to assess effects of antiarrhythmic drugs at certain pointsduring a course of drug use and may be used for performing a highresolution electrocardiographic analysis.

The systems described above with reference to FIGS. 1 and 2 allow arapid assessment of the three-dimensional positions of the vestelectrodes, i.e. of the surface electrodes, by means of optical shapesensing localization and the assessment of the three-dimensional cardiacanatomy in relation to the three-dimensional positions of the vestelectrodes by means of a transthoracic or transesophageal echo probethat is localized in the three-dimensional space by means of opticalshape sensing localization. The systems can be used as an advancedelectrocardiography tool with epicardial activation diagnosiscapabilities.

Preferentially, the configuration of the electrodes in theelectrocardiography mapping vest within the vest fabric is known. In anembodiment, in particular in the embodiment described above withreference to FIG. 1, within the vest are a plurality of landmark points,i.e. reference marks, that can be visually identified, for instance, byhaving a certain color and/or shape. The positions of electrodes inrelation to the landmark points are known as well. After putting on thevest to the person the three-dimensional positions of the landmarkpoints can be determined by touching the landmarks by means of the wandequipped with the optical shape sensing sensor. The number anddistribution of the landmark points are preferentially such that therelative positions of all electrodes in relation to the landmarks andtherefore in relation to a frame of reference can be calculated based onthe known positions of the electrodes within the fabric and in relationto the landmarks. To avoid person motion distortion, one or moreadditional optical shape sensing sensors can be temporally added to thevest or attached to patches that are put somewhere on the patient'sthorax to compensate for the person movement.

Preferentially, the ultrasound unit is used for reconstructing atransthoracic or transesophageal three-dimensional representation of theperson's cardiac anatomy. This reconstruction can be based onthree-dimensional imaging of the heart and subsequent segmentation ofthe cardiac structures or by matching a generalized three-dimensionalcardiac model to the three-dimensional ultrasound image, whereinoptionally the generalized three-dimensional cardiac model can bedeformed. The ultrasound probe is equipped with optical shape sensinglocalization as well, thus allowing to correlate the three-dimensionalcardiac anatomy with the vest electrode positions. In an embodiment theultrasound based cardiac anatomy assessment is performed before or afterthe vest electrodes positions assessment. In both cases optical shapesensing sensors temporally added to the vest or attached to a patch thatis put somewhere on the patient's thorax can be used to relate theultrasound probe position and therefore the three-dimensional cardiacanatomy to the vest electrode positions.

In an embodiment, in particular in the embodiment described above withreference to FIG. 2, the electrode vest can be equipped with one or moreoptical shape sensing fibers, wherein the positions of the vestelectrodes are identified and therefore known in relation to the one ormore optical shape sensing fibers. Through assessing thethree-dimensional shape of the one or more optical shape sensing fibersthe three-dimensional positions of the vest electrodes can becalculated. Also in this embodiment the position of the cardiac anatomyis determined as described above by using an ultrasound probe, whereinin this embodiment the position of the ultrasound probe is registeredwith the position of the vest electrodes by using the optical shapesensing signals from the one or more optical shape sensing fibers withinthe vest and from the optical shape sensing sensor of the ultrasoundprobe.

Although in the embodiment described above with reference to FIG. 1 anadditional wand 4 equipped with an optical shape sensing fiber 6 is usedfor determining the three-dimensional positions of reference marks 2, inanother embodiment this additional wand 4 with the optical shape sensingfiber 6 is not needed. Instead, the ultrasound probe 22 can be used fordetermining the three-dimensional positions of the reference marks 2.Thus, a user like a physician can move the ultrasound probe 22 fromreference mark to reference mark, in order to determine thethree-dimensional positions of these reference mark by optical shapesensing localization. These three-dimensional positions of the referencemarks are then used by the surface electrodes position calculation unitfor determining the three-dimensional positions of the surfaceelectrodes as described above. The same ultrasound probe 22 can then beused for providing an ultrasound signal being indicative of the cardiacstructure, in particular, being indicative of the epicardial surface, inorder to determine the position of the epicardial surface.

The ultrasound probe is preferentially used through an opening in thevest directly on the skin of the thorax, or before the vest is put on bythe person. In the embodiment described above with reference to FIG. 1,the ultrasound probe 22 may be used on the skin of the thorax foracquiring an ultrasound image of the heart before the vest is put on bythe person, but after a reference patch being connected to an opticalshape sensing fiber for determining the position of the reference patchis applied to the skin of the thorax.

The locations of the surface electrodes of the vest can be determined bymeans of Fiber Optic Shape Sensing and Localization (FOSSL) technology,for example, based on Fiber Bragg Gratings. The vest may contain one ormore fibers with such grating that allow the full three-dimensionalshape and location of the fibers to be determined. By knowing thespatial relation between each of the surface electrodes and a relevantfiber, the location of each of the electrodes can be determined. Thiscan then be realized without any x-ray or magnetic resonance basedlocalization of the surface electrodes. Moreover, the ultrasound probecan be a three-dimensional transesophageal or micro transthoracicultrasound probe which can be used to reconstruct the heart.Furthermore, the FOSSL technology can be used to localize the probe bymeans of such a fiber, in particular, in a catheter. The FOSSLtechnology can be used to localize the surface electrodes as describedabove.

The systems described above with reference to FIGS. 1 and 2 provide anelectrocardiographic mapping based on a three-dimensional assessment ofvest electrode positions by means of optical shape sensing localizedvest electrodes and based on a three-dimensional cardiac anatomyassessment of optical shape sensing localized ultrasound imaging. Thesystem can therefore provide an electrocardiographic diagnostic toolthat can be used for obtaining, for instance, pre-interventional andpost-interventional information that is not obtainable by knownelectrocardiographic systems. For example, information can be providedsuch as reasonably accurate positions of ectopic foci, reasonableaccurate positions of ventricular re-entries, information thatdistinguishes between re-entry or focal ventricular tachycardia and itslocalizations, information about re-connection of pulmonary veinconduction and localization of culprit pulmonary veins, in order to beat least able to distinguish between left and right pulmonary veins, andinformation about effects of antiarrhythmic drugs, in particular, ofchanges in use of antiarrhythmics drugs.

Although in above described embodiments, in particular, in FIGS. 1 and2, the vest has a certain distribution of electrodes, it should be notedthat the electrodes in the vest are only schematically and exemplarilyindicated in FIGS. 1 and 2, i.e., for instance, they can be distributeddifferently within the vest. The vest preferentially comprises severalhundreds of the electrodes covering the entire thorax of the person.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality.

A single unit or device may fulfill the functions of several itemsrecited in the claims. The mere fact that certain measures are recitedin mutually different dependent claims does not indicate that acombination of these measures cannot be used to advantage.

Calculations like the calculation of the surface electrodes positions,the calculation of the cardiac structure position, the calculation ofthe electrical activity map and/or the analysis of the electricalactivity map performed by one or several units or devices can beperformed by any other number of units or devices. The calculationsand/or the analysis of the electrical activity map and/or the control ofthe system for providing an electrical activity map in accordance withthe method for providing an electrical activity map can be implementedas program code means of a computer program and/or as dedicatedhardware.

A computer program may be stored/distributed on a suitable medium, suchas an optical storage medium or a solid-state medium, supplied togetherwith or as part of other hardware, but may also be distributed in otherforms, such as via the Internet or other wired or wirelesstelecommunication systems.

Any reference signs in the claims should not be construed as limitingthe scope.

The invention relates to a system for providing an electrical activitymap of the heart of a living being by means of electrical signals fromthe heart acquired by a plurality of surface electrodes being arrangedon an outer surface of the living being. A surface electrodes positionsdetermination unit determines positions of the plurality of surfaceelectrodes by means of optical shape sensing localization and anelectrical activity map determination unit determines the electricalactivity map at the cardiac structure based on the measured electricalsignals, the determined positions of the plurality of electrodes and aposition of a cardiac structure, in particular, of the epicardialsurface. Since optical shape sensing is used for determining thepositions of the plurality of surface electrodes and not, for instance,x-rays, the electrical activity map can be determined, withoutnecessarily applying an x-ray radiation dose.

1-13. (canceled)
 14. A vest for being worn by a living being, the vestbeing adapted to be used for providing an electrical activity map, thevest comprising: a plurality of surface electrodes for being arranged onan outer surface of the living being, when the vest is worn by theliving being, and for acquiring electrical signals from the heart of theliving being, an optical shape sensing fiber for generating an opticalshape sensing signal being indicative of the three-dimensional shape ofthe optical shape sensing fiber and for providing the optical shapesensing signal to a surface electrodes positions calculation unit.
 15. Asystem for providing an electrical activity map of the heart of a livingbeing by means of electrical signals from the heart acquired by aplurality of surface electrodes being arranged on an outer surface ofthe living being, wherein a vest as defined in claim 14 is worn by theliving being and comprises the plurality of surface electrodes, thesystem comprising: a spatial relation providing unit for providingspatial relations between an optical shape sensing fiber of the vest andthe surface electrodes, a surface electrodes positions calculation unitfor calculating the positions of the surface electrodes depending on thethree-dimensional shape of the optical shape sensing fiber as indicatedby an optical shape sensing signal provided by the optical shape sensingfiber and the provided spatial relation, a cardiac structure positiondetermination unit for determining a position of a cardiac structure ofthe living being, wherein the cardiac structure position determinationunit comprises a cardiac structure position calculation unit forcalculating the position of the cardiac structure based on a) anultrasound signal received from an ultrasound unit equipped with anoptical shape sensing sensor, wherein the ultrasound signal isindicative of the position of the cardiac structure, and b) an opticalshape sensing signal received from the optical shape sensing sensor ofthe ultrasound unit, wherein the optical shape sensing signal isindicative of the position of the ultrasound unit, an electricalactivity map determination unit for determining the electrical activitymap at the cardiac structure based on the electrical signals measured onthe outer surface of the living being, the determined positions of theplurality of electrodes and the determined position of the cardiacstructure.
 16. The system as defined in claim 14, wherein the cardiacstructure position determination unit comprises the ultrasound unit forgenerating the ultrasound signal being indicative of the position of thecardiac structure, wherein the ultrasound unit is equipped with theoptical shape sensing sensor for generating the optical shape sensingsignal being indicative of the position of the ultrasound unit.
 17. Thesystem as defined in claim 14, wherein the ultrasound unit is atransthoracic echo probe or a transesophageal echo probe.
 18. The systemas defined in claim 14, wherein the ultrasound signal represents anultrasound image and wherein the cardiac structure calculation unit isadapted to detect the cardiac structure in the ultrasound image and tocalculate the position of the cardiac structure based on the cardiacstructure detected in the ultrasound image.
 19. A method for providingan electrical activity map of the heart of a living being by means ofelectrical signals from the heart acquired by a plurality of surfaceelectrodes being arranged on an outer surface of the living being, themethod comprising: determining positions of the plurality of surfaceelectrodes, wherein a vest as defined in claim 14 is worn by the livingbeing and comprises the plurality of surface electrodes, wherein spatialrelations between an optical shape sensing fiber of the vest and thesurface electrodes are provided by a spatial relation providing unit,and wherein the positions of the surface electrodes are calculateddepending on a three-dimensional shape of the optical shape sensingfiber as indicated by an optical shape sensing signal provided by theoptical shape sensing fiber and the provided spatial relation by asurface electrodes positions calculation unit, determining a position ofa cardiac structure of the living being, wherein the position of thecardiac structure is determined based on a) an ultrasound signalreceived from an ultrasound unit equipped with an optical shape sensingsensor, wherein the ultrasound signal is indicative of the position ofthe cardiac structure, and b) an optical shape sensing signal receivedfrom the optical shape sensing sensor of the ultrasound unit, whereinthe optical shape sensing signal is indicative of the position of theultrasound unit, by an cardiac structure position calculation unit,determining the electrical activity map at the cardiac structure basedon the electrical signals measured on the outer surface of the livingbeing, the determined positions of the plurality of electrodes and thedetermined position of the cardiac structure by an electrical activitymap determination unit.
 20. A computer program for providing anelectrical activity map of the heart of a living being by means ofelectrical signals from the heart acquired by a plurality of surfaceelectrodes being arranged on an outer surface of the living being, thecomputer program comprising program code means for causing a system asdefined in claim 14.